Anti-twist device

ABSTRACT

The embodiments described and claimed herein relate to opening in a housing for a retractor. The opening includes structures which reduce the risk of twisting webbing passing through the opening and, thereby, interfering with the proper functionality of the retractor. The openings can include one or more guide surfaces which incorporate some combination of features which smooth out the webbing as it enters the retractor and/or urge the webbing into alignment with the retractor opening. In addition, or in the alternative, the height of the opening can be modified to closely conform to the maximum thickness of the webbing. The guide surfaces can be integrally formed with the retractor housing or can be provided by an insert piece which attaches to the housing. In one embodiment, the guide surface is disposed along an upper wall of the opening and is curvilinear and outwardly diverging. More specifically, the guide surface has slopes that vary along its length whereby the guide surface is approximately vertical near a leading edge of the guide surface and is approximately horizontal near a trailing edge of the guide surface.

FIELD OF THE INVENTIONS

The embodiments described and claimed herein relate generally towheelchair securement devices for vehicles. More specifically, oneembodiment described herein relates to a retractor cover, which includesfeatures to prevent twisted webbing or restraint strap from passing intothe retractor housing. Another embodiment relates to a retrofit insertfor a retractor cover, which includes similar anti-twist features. Yetanother embodiment relates to an anti-twist guide slot, or retrofitinsert for a slot, which could be used in a location remote from theretractor.

BACKGROUND OF THE INVENTIONS

Retractors are utilized in a number of different applications, such assafety harnesses, automobile seatbelt systems, and wheelchair securementsystems for vehicles. The particular embodiments disclosed herein areprimarily adapted for use in wheelchair securement systems forrestraining both the wheelchair and the wheelchair passenger, althoughit is envisioned that the features shown and described herein could beutilized in an equally effective manner in other applications.

It is well known that retractors can be installed in a number ofdifferent configurations. In a most simple application, four retractorscan be mounted to a vehicle's floor or near thereby, one for securingeach corner of a wheelchair. For examples of prior art retractors, seeQ′Straint's QRT retractors at www.qstarint.com and Sure-Lok's RetraktorSeries System at www.sure-lok.com. Since floor-mounted retractors canpresent serious tripping hazards for vehicle passengers, manufacturershave developed various apparatus for reducing or minimizing the trippinghazard. For example, as described in U.S. patent application Ser. No.11/776,223, which is incorporated herein by reference, Q'Straint hasdeveloped a retractable wheelchair anchor onto which two retractors canbe mounted. Q'Straint's wheelchair anchor includes a foot-operatedtelescoping arm, which retracts into a non-use position to present alesser tripping hazard than floor-mounted retractors. See also AmericanSeating's Advanced Restraint Module (“A.R.M.”) atwww.americanseating.com. Q'Straint has also developed a forward facingbarrier system as disclosed in U.S. patent application Ser. No.11/847,435, which is incorporated herein by reference. Q'Straint'sforward facing barrier includes a housing for concealing internallymounted retractors, whereby the webbing from each retractor passesthrough a corresponding slot in the barrier housing.

In wheelchair securement applications, retractors often include up toseveral feet of webbing. At its proximal end, the webbing is attached toa spring loaded spool which is disposed within a cover or housing. Atits free end, the webbing is typically attached to an anchor (such as anS-hook or J-hook), which is adapted to engage with a structural memberof a wheelchair, thereby securing the wheelchair. Alternatively, thewebbing can be adapted for use as a lap or shoulder belt for thewheelchair passenger and, for such applications, can include some sortof a connector, such as a male, female, or pin connector.

When used in exposed applications—for example, if the retractors arefloor-mounted or mounted onto a retractable wheelchair anchor—theretractor will usually include a metal or plastic cover for housing andprotecting the working components of the retractor. When used innon-exposed applications—such as when mounted internal to the barrierhousing—use of a zinc cover is prohibitively expensive. For this reason,manufacturers often will not use a separate cover (or housing) for theretractor and will instead rely upon the barrier housing to protect theretractor. Alternatively, manufacturers may use an inexpensive cover,such as a plastic one.

While all current wheelchair retractors are vulnerable to twists in thewebbing, self-locking retractors are particularly so since they haveopenings which are relatively large, having an effective height which isgenerally more than ten (10) times the thickness of the webbing itself.The openings are large since self-locking retractors utilize a doublestitched portion of webbing, which must be passed through the opening toenable the self-locking feature. The double stitched portion of webbingis simply the free end of the webbing that is looped through the anchor,folded back over itself, and stitched together. When the webbing isfully retracted, a length of double stitched webbing is wound on theretractor spool such that it triggers a locking bar. In thisconfiguration, the retractor is “unlocked,” such that the webbing can befreely pulled out of the retractor. When the double stitched portion ofwebbing is pulled out of the retractor, the locking bar is released, butdoes not fully engage (i.e., to prevent further extension of thewebbing) until the attendant stops pulling on the webbing and allows theself-tensioning feature of the retractor to retract a small amount ofwebbing.

In typical use of any of the above described wheelchair securementsystems, an attendant (or vehicle operator) grasps and pulls the anchor(or lap and shoulder belt connectors), thereby drawing webbing out fromthe retractor spool, and attaches the anchor to a structural member ofthe wheelchair (or attaches the lap and shoulder belts together). Oftentimes, the attendant will introduce twists into the webbing which maynot be “undone” when the anchor is released from the wheelchair (or thelap belt is released). The twist may pass through the housing and becomewound onto the retractor spool (note that, for the above describedwheelchair securement systems, the term housing refers to either or boththe retractor cover and barrier housing). Once the twist is wound ontothe retractor spool, the twist can interfere with proper functioning ofthe retractor such that the efforts required to pull the webbing fromthe retractor are increased. Moreover, the twist may cause the webbingto overlap the gears, which in turn causes accelerated wear of thewebbing and could possibly jam the retractor. Sometimes, it may beimpossible to extend the webbing without disassembling the retractor orthe barrier. In such cases, the retractor will not work and, hence, thesecurement system will be unusable.

Wheelchair securement system manufacturers, being aware of and until nowbeing unable to solve these problems, instruct their customers toregularly inspect for twists in the webbing. Ideally, a vehicle operatorwill inspect the webbing for twists every time before securing awheelchair. In the case of mass transit vehicles, this additional stepincreases the dwell time at stops and increases the risk of the operatorsuffering from a back injury.

SUMMARY OF THE INVENTIONS

The embodiments described and claimed herein at least partially reducethe risk of twisting. As discussed briefly above, it is believed thatthe configuration (i.e. size and or shape) of the prior art openings (orguide slots) allow the twists to pass through unimpeded. Therefore, theopenings shown and described herein incorporate some combination offeatures which smooth out the webbing as it passes through the openingand/or urge the webbing into alignment with the opening. In this manner,the embodiments described, shown, and claimed herein reduce the chancesthat the webbing will fold over into a double thickness and become woundonto the retractor spool.

For example, one embodiment described herein is a housing for aretractor. The housing, in turn, defines an interior space in which theworking components of the retractor are disposed and has an openingwhich is adapted for passing webbing therethrough. The opening in thehousing has at least one guide surface which is integrally formedtherein. The guide surface is configured to guide the movement of thewebbing and thereby resist the passing of twists in the webbing throughthe opening. More specifically, the guide surface has a leading edgebeing disposed generally near an outside the housing, a trailing edge,and at least one slope therebetween, wherein the at least one slopecauses the leading edge to diverge from the opening. In anotherembodiment, the housing for the retractor is a retractor cover. In yetanother embodiment, the retractor is internally mounted in a barrier,whereby the housing for the retractor is a barrier housing.

Another embodiment described herein is a retrofit insert piece orwebbing guide which is adapted to attach to a housing for a retractorand which provides at least one guide surface for the opening in thehousing. Like the guide surface of the first embodiment, the guidesurface of the second embodiment serves to resist a twist in the webbingfrom passing through the opening. More specifically, at least a portionof the guide surface is aligned in non-parallel relation to the axis ofthe opening, whereby the portion the guide surface is outwardlydiverging. In another embodiment, the housing for the retractor is aretractor cover. In yet another embodiment, the retractor is internallymounted in a barrier, whereby the housing for the retractor is a barrierhousing.

Other embodiments, which include some combination of the featuresdiscussed above and below and other features which are known or unknownin the art, are contemplated as falling within the claims even if suchembodiments are not specifically identified or discussed herein.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features, aspects, objects, and advantages of theembodiments described and claimed herein will become better understoodupon consideration of the following detailed description, appendedclaims, and accompanying drawings where:

FIG. 1 is a perspective view of a first embodiment of a retractorhousing, which includes integrally formed guide surfaces at the openingof the housing;

FIG. 2 is a first perspective, exploded view of the same;

FIG. 3 is a second perspective, exploded view of the same;

FIG. 4 is a cross sectional view of the same;

FIG. 5 is a top view of a lower member of the retractor housing;

FIG. 6 is a bottom view of an upper member of the retractor housing;

FIG. 7 is a perspective view of a second embodiment of a retractor,which includes a retrofit webbing guide;

FIG. 8 is a perspective view of the retrofit webbing guide;

FIG. 9 is a front view of the same;

FIG. 10 is a bottom view of the same;

FIG. 11 is a cross sectional view of the same;

FIG. 12 is a perspective view of the second embodiment of the retractor,which the retrofit webbing guide partially inserted into the opening inthe retractor housing;

FIG. 13 is a cross-sectional view of the first embodiment of theretractor housing, showing the relative location of the upper guidesurface with the internal mechanisms of the retractor;

FIG. 14 is a cross-sectional view of the second embodiment of theretractor housing, showing the relative location of the retrofit insertwith the internal mechanisms of the retractor;

FIG. 15 is a forward facing barrier which includes anti-twist guideslots for wheelchair securement and lap and shoulder belt retractors;

FIG. 16 is a close-up view of the same showing the anti-twist guideslots for the wheelchair securement and lap belt retractors;

FIG. 17 is a close-up view of the same showing the anti-twist guideslots for the shoulder belt retractor; and,

FIG. 18 is a perspective view of a second embodiment of a retrofitwebbing guide.

It should be understood that the drawings are not necessarily to scaleand that the embodiments are sometimes illustrated by graphic symbols,phantom lines, diagrammatic representations and fragmentary views. Incertain instances, details which are not necessary for an understandingof the embodiments described and claimed herein or which render otherdetails difficult to perceive may have been omitted. It should beunderstood, of course, that the inventions described herein are notnecessarily limited to the particular embodiments illustrated. Indeed,it is expected that persons of ordinary skill in the art may devise anumber of alternative configurations that are similar and equivalent tothe embodiments shown and described herein without departing from thespirit and scope of the claims.

Like reference numerals will be used to refer to like or similar partsfrom Figure to Figure in the following detailed description of thedrawings.

DETAILED DESCRIPTION OF THE DRAWINGS

Various embodiments of an anti-twist slot or opening for passing webbingtherethrough are described and shown herein which incorporate somecombination of features which substantially reduce the chance thattwisted webbing will become wound onto a retractor spool and thereforeinterfere with the functionality of a retractor. Some of the features ofthe openings which make this possible relate to the height of theopening as compared to the thickness of the webbing, the length of theinnermost guide surface on the upper wall (or various other wallsdepending upon orientation), the proximity of the innermost guidesurface on the upper wall (or various other walls depending uponorientation) to the retractor spool, the aspect ratios of the opening,and/or the contours of the opening side walls. Although the embodimentsdepicted herein include openings having specific aspect ratios andspecific contours, it is in no way intended that the inventions belimited to those specific values or those specific combinations ofaspect ratios and contours. The specific dimensions recited herein arefor example purposes only and apply only to the specific embodimentsshown in the figures. The dimensions are not intended to be limitingupon the claims except to the extent that specific dimensions areexplicitly recited therein. Indeed, the dimensions could vary widely(even outside the specific ranges provided herein) depending on variousfactors, including the type of application, the length and thickness ofthe webbing, etc.

Referring first to FIGS. 1-6 and 13, a first embodiment of a housing 10for a retractor is depicted. The retractor housing 10 of the firstembodiment is a retractor cover and comprises an upper member 20 and alower member 30, which are adapted to engage and thereby form anenclosure. Although not all components are shown, the housing isintended to enclose and protect the various working components of theretractor, including a spring loaded spool mechanism 22, which in turncarries webbing 14. Although the housing 10 is comprised of two members20, 30, it is contemplated that the housing 10 could be defined by moreor less members.

The upper member 20 and lower member 30 merge to define an opening 40,through which the webbing is intended to pass. The opening 40 can be anyshape (for example, such as oval or hexagonal), but as shown isgenerally quadrangular wherein the opening 40 is defined by four sidewalls 50, 60, 70, 80. The four sidewalls 50, 60, 70, 80 are guidesurfaces and, as shown, are generally curvilinear and inwardly convergetowards each other (or, in other words, outwardly diverge). Although allfour sidewalls 50, 60, 70, 80 of the shown embodiment are configured asguide surfaces, it is contemplated that less than all of the side wallscould be configured as such. In fact, configuring the opening with asingle guide surface may be sufficient.

For purposes of this description, it is assumed that the retractorhousing 10 is horizontally oriented. Therefore, the first sidewall 50 isreferred to herein as an upper sidewall 50, the second sidewall 60 isreferred to herein as a lower sidewall 60, the third sidewall 70 isreferred to herein as a left sidewall, and the fourth sidewall 80 isreferred to herein as a right sidewall. However, since it iscontemplated that the retractor housing 10 could be oriented verticallyor in an inclined configuration, the use of the terms upper and lowerare used for purposes of description and not for purposes of definingthe relative location of these walls when the retractor housing isinstalled.

The upper sidewall 50, as shown, includes several guide surfaces orportions and is both curvilinear and inwardly converging, although it iscontemplated that the upper sidewall 50 could be entirely linear, orinclude linear portions. As best shown in FIG. 4, the upper sidewall 50has slopes that vary along its length (i.e., in the direction of travelof the webbing) and, as shown, has an inner portion 52 and an outerportion 54. Starting from an inner extent of the inner portion 52 andmoving outwardly, the inner portion 52 is approximately linear andparallel with the axis of the opening and/or the general plane alongwhich the webbing travels, although it is contemplated that the innerportion 52 could be curvilinear and oriented an angle to the axis of theopening. The intersection 56 between the inner portion 52 and the outerportion 54 is characterized by a substantial increase in slope along itslength. In that respect, the upper sidewall 50 begins to diverge fromthe lower side wall 60 near or at the intersection 56. The intersection56 has an approximate radius of 0.20″, although radii in the range ofapproximately 0.1″ to 0.3″ would also be sufficient. The upper sidewall50 continues to diverge from the lower sidewall along the length of theouter portion 54, although to a much greater extent than at theintersection 56. The outer portion 54 is marked by a gradual increase inslope and, at an outer extent, approaches approximately vertical. Theouter portion 54 has a radius of approximately 0.30″ near its midpoint,although a radius of approximately 0.20″ to 0.40″ would also besufficient.

For a horizontally oriented retractor, it has been found that the uppersidewall 50 contributes more significantly to the anti-twist capabilityof the retractor housing, than do the other sidewalls 60, 70, 80. It hasalso been found that some features of the upper wall 50 contribute moresignificantly to the anti-twist capability of the retractor. Forexample, it is believed that better results can be obtained bymaximizing the length of the inner portion of the upper sidewall 50 andpositioning the inner extent of the inner portion 52 as near as possibleto the spool mechanism or the webbing which is wound thereon. In fact,for a horizontally oriented retractor, it is believed that satisfactoryresults could be obtained by merely configuring the upper wall as aplanar surface which extends a distance from an outside surface of theretractor housing into the opening.

Like the upper sidewall 50, the lower sidewall 60, as shown, is bothcurvilinear and inwardly converging. As best shown in FIG. 4, the lowersidewall 60 has slopes that vary along its length and, as shown, has aninner portion 62 and an outer portion 64. Starting from the inside ofthe housing 10 and moving outwardly, the inner portion 62 issubstantially parallel with the axis of the opening and/or the generalplane along which the webbing travels. The intersection 66 between theinner portion 62 and the outer portion 64 is characterized by asubstantial decrease in slope along its length. In that respect, thelower sidewall 60 begins to diverge from the upper side wall 56 near orat the intersection 66. The intersection has an approximate radius of0.34″, although a radius in the range of approximately 0.24″ to 0.44″would also be sufficient. The lower sidewall 60 continues to divergefrom the upper sidewall 50 along the length of the outer portion 64,although to a slightly greater extent than at the intersection 66. Theouter portion 64 is marked by a gradual decrease in slope and, at anouter extent, passes through vertical.

The left and right sidewalls 70, 80 are essentially mirror images ofeach other. For that reason, only the left sidewall 70 is described indetail herein. As best shown in FIG. 5, the left sidewall 70 (like boththe upper and lower sidewalls 50, 60) is both curvilinear and inwardlyconverging. Moreover, the left sidewall 70 includes an inner portion 72and an outer portion 74, which merge at an intersection 76. The lengthof the inner portion 72 is aligned substantially parallel with thedirection of travel of the webbing and/or the axis of the opening, whilethe outer portion diverges away from the axis of the opening at an angleof approximately 32 degrees. It is contemplated, however, that the outerportion could be oriented at other angles, such as between approximately30 degrees to 45 degrees. The intersection 56, as shown, has a radius ofapproximately 0.20″ although a radius in the range of 0.10″ to 0.30″would also be sufficient.

The outer portions 54, 64, 74, 84 of the sidewalls 50, 60, 70, 80 can becharacterized as smoothing surfaces. Since these portions 54, 64, 74, 84of the sidewalls are marked by gradual changes in slope and/or generallydiverge from the axis of the opening, it is believed that these surfacesexert only low to moderate untwisting forces on the webbing. The innerportions 52, 62, 72, 82 and/or the intersections 56, 66, 76, 86 of thesidewalls 50, 60, 70, 80 can be characterized as urging surfaces, asthey are marked by a greater change in slope and/or are substantiallyparallel with the axis of the opening. It is believed that the urgingsurfaces are more capable of exerting greater untwisting forces on thewebbing. When both are present, the smoothing and urging surfacescooperatively work to prevent twisted webbing from passing through theopening 40.

In additional or in the alternative to the various contours of thesidewalls 50, 60, 70, 80, it is believed that the aspect ratios of theopening 40 contribute to the untwisting capabilities of the retractorhousing 10. The opening 40 can be characterized as having majordimensions of W₁×H₁ and minor (or effective) dimensions of W₂×H₂. Atsome point along the depth D of the opening 40, there is an intermediateplane where the opening 40 has intermediate dimensions which areapproximately equal to or slightly greater than the minor dimensions.The intermediate plane occurs at a depth D1 from the outer extent of theopening 40. The location of the intermediate plane approximatelycorresponds with the location of the intersections 56, 66, 76, 86, atthe point at which the opening 40 begins to substantially divergeoutwardly. In the shown embodiment, W₁ is approximately equal to 2.3″,W₂ is approximately equal to 1.96″, H₁ is approximately equal to 1″, H₂is approximately equal to 0.24″, D is approximately equal to 0.40″, andD1 is approximately equal to 0.20″. It must be kept in mind, asdiscussed in more detailed above, that the dimensions recited herein canvary substantially without affecting the anti-twist capabilities.

It is believed that the extent to which the opening is capable ofinducing smoothing and urging actions on the webbing can be measured byvarious aspect ratios, including the major to minor height and widthratios and various other ratios (which can be easily calculated from thedimensions provided above or scaled from the attached figures).

The major to minor height ratio H₁:H₂, as shown, is approximately 4:1,although a major to minor height ratio of approximately 3:1 to 5:1 wouldalso be sufficient. The major to minor width ratio W₁:W₂, as shown, isapproximately 1.17:1, although a major to minor width ratio ofapproximately 1:1 to 1.7:1 would also be sufficient. As the height andwidth ratios approach 1, the opening is likely imparting more of anurging action than a smoothing action on the webbing. In contrast, asthe height and width ratios approach infinity, the opening is likelyimparting more of a smoothing action than an urging action. In additionor in alternative to providing the opening 40 with any combination ofthe features described above, conforming the opening 40 of the retractorhousing 10 to satisfy at least some of these parameters will contributeto anti-twist capabilities of the opening.

It is further believed that the anti-twist capabilities of the shownembodiments are enhanced due to the dimensional relationship of theopening height with the webbing thickness. For comparison purposes, thethickness of typical webbing (or restraint strap), is approximately 1.2mm. When folded over into double thickness and stitched together, thewebbing will have a thickness of around 2.4 to 2.5 mm. With H₂ equal to5.59 mm, it is understood that the effective height of the opening,being slightly greater than the thickness of double stitched webbing(about 2.2 times greater than a double stitched portion or about 4.7times greater than single thickness webbing), allows a double stitchedportion of webbing to pass into the opening. It has been found that byclosely conforming the height of the opening with the maximum thicknessof webbing in the manner described above (i.e., for the shownembodiments, the thickness of a double stitched portion), there is areduced chance that an unintended folded over portion of webbing willenter the retractor. It is believed that satisfactory results can beobtained by reducing the effective height of the opening such that it isless than ten times the thickness of the webbing. It has been observed,however, that the ability of the opening to resist the passing of twistsexponentially increases by decreasing the effective height of theopening, where the best results can be obtained with an opening that hasan effective height which is approximately equal to the thickness of adouble stitched portion of webbing (i.e., approximately two times thethickness of the webbing). Ideally, the opening will have an effectiveheight which is between approximately two (2) to six (6) times thethickness of the webbing itself.

Referring now to FIGS. 7-12 and 14, a second embodiment of a retractor110 is shown. The second embodiment of the retractor 110 can besubstantially similar to prior art retractors, in that it comprises ahousing 112 for enclosing and protecting the working components of theretractor, including a spool mechanism 116, and having a quadrangularopening 140 through which webbing 114 is adapted to pass. Where thesecond embodiment of the retractor 110 differs from the prior art is itsinclusion of a retrofit anti-twist insert (or member) 145, whichmodifies the size and shape of the opening 140 with the aim to reducethe chance that twisted webbing will pass into the retractor housing112. Although the anti-twist insert 145 is designed to be easilyinstalled by end-users as an after-market component to providepre-existing retractor housings with anti-twist capability, otherconfigurations are contemplated which may require a skilled technicianfor installation.

For practical reasons, the insert 145 is shaped like a “U” and,therefore, has three sections 155, 175, 185. This construction allowsthe insert piece 145 to be installed around the webbing, therebynegating the need to disassemble the retractor and feed the webbingthrough the insert piece. Although the convenience of a three sidedretrofit piece 145 is recognized herein, it is by no means asserted thatit would be impossible or prohibitively difficult to utilize afour-sided piece or that the claims herein do not cover such anembodiment. Indeed, it is contemplated that a four-sided retrofit piececould be made which would require the end-user (or maintenance personal)to disassemble the retractor 110 and feed the webbing 114 through theretrofit piece. Alternatively, the retrofit piece could comprise twosections, one of which is installed on one side of the webbing 114 andthe other of which is installed on the other side of the webbing 114.Yet another alternative embodiment is shown in FIG. 18. The secondembodiment of the retrofit piece 345 is four-sided, having foursidewalls 350, 360, 370, 380, each of which could include a guidesurface. One of the sides 380 includes a cut 385, through which thewebbing can be inserted. Utilizing the elasticity of the retrofit piece345, a gap can be formed at the cut 385 by grasping the piece 345 fromopposite sides of the cut 385 and pulling in the directions indicationby the arrows in FIG. 18. When the piece 345 is manipulated in such amanner, the opposite side 370 acts as a hinge to allowing a gap to beformed at the cut 385, whereby the webbing can be slid into the openingof the retrofit piece 345.

Referring again to the embodiment shown in FIGS. 7-12 and 14, the firstembodiment of the retrofit insert piece 145 includes at least one guidesurface 150, which in the shown embodiment is present on the uppersection 155. It is contemplated that, in combination or in thealternative, the side sections 175, 185 could include similar guidesurfaces. In addition, for a four sided retrofit insert piece (notshown) one or more, or even all, sides could include guide surfaces.See, for example, the guide surfaces provided by the first embodiment ofthe retractor housing 10. It should be noted that the particular housing112 disclosed in the figures includes an opening that is notsufficiently wide to include guide surfaces on the side sections 175,185. Inclusion of guide surfaces on the side sections 175, 185 wouldreduce the width of the opening to the point of buckling the webbing.

The guide surface 150 is shown as curvilinear and inwardly converging,although it is contemplated that the guide surface could be planarand/or discontinuous, just like the guide surfaces 50, 60, 70, 80 of theprevious embodiment. As best shown in FIG. 11, the guide surface 150 hasslopes that vary along its length (i.e., along the direction of travelof the webbing) and, as shown, has an inner portion 152 and an outerportion 154. Starting from an inner extent of the inner portion 152 andmoving outwardly, the inner portion 152 begins as nearly parallel withthe direction of travel of the webbing (see FIG. 14) and graduallyincreases in slope. In that respect, the upper guide surface 150diverges from the lower wall of the opening 140. The intersection 156between the inner portion 152 and the outer portion 154 is characterizedby a more substantial increase in slope along its length. Theintersection has an approximate radius of 0.14″, although the radiuscould vary widely with similar results. The upper sidewall 150 continuesto diverge from the lower wall of the opening 140 along the length ofthe outer portion 154, although to a much greater extent. The outerportion 154 is marked by a gradual increase in slope and, at an outerextent, approaches approximately vertical. The outer portion 154 has aradius of approximately 0.13″ near its midpoint, although the radiuscould vary widely with similar results.

In addition or in the alternative to changing the contour of the opening140, the insert piece 145 contributes to the untwisting capabilities ofthe retractor housing 112 by modifying the aspect ratios of the opening140. Conforming the insert 145 to satisfy at least some of theparameters provided above for the first embodiment will contribute toanti-twist capabilities of the opening.

The insert piece 145 includes multiple locking grooves 151, 172, 174,182, 184 which are adapted to engage with the periphery of the opening140. In the shown embodiment, the locking groove 151, 172, 174, 182, 184are essentially narrow channels which are adapted to receive thethin-wall construction of the retractor housing 112 which surrounds theopening 140. The first (or top) section 155 of the insert piece 145includes one generally elongated locking groove 151 which is adapted toengage with the upper wall of the opening 140. Both the second and third(or right and left side) sections 175, 185 include two locking grooves172, 174, 182, 184 which are adapted to engage with the side walls andlower wall of the opening 140. The locking grooves 151, 172, 174, 182,184 are generally bounded by an outer lip 157, 177, 187 and inner lips159, 179, 189. In the shown embodiment, the outer lip 157, 177, 187continuously extends around the periphery of the insert 145 and hasouter dimensions which exceed that of the opening 140. In that respect,the inside surface of the lip 157, 177, 187 rests against the outsidesurface of the retractor housing 112 and thereby frames the opening 140.The inner lips 159, 179, 189 are discontinuous to reduce the forcerequired to install the retrofit insert 145. However, it is contemplatedthat the outer lip 157, 177, 187 could be discontinuous and/or the innerlips 159, 179, 189 could be continuous.

As best shown by FIG. 12, the insert piece 145 is configured to beinstalled, at least in part, by “snapping.” First, the insert piece 145is tilted such that the upper locking groove 151 engages with the upperwall of the opening 140. Then, the lower edge of the insert piece 145 isrotated into engagement with the lower wall of the opening 140. Moderateforce may be required to snap the lower and side edges of the insertpiece 145 into engagement with the opening. To reduce the requiredinstallation force, the inner lips 179, 189 have chamfered rear edges.

Although the insert component 145 is characterized as a retrofit piece,and it was initially intended that it be used with existing retractorsto provide anti-twist capabilities, it is not necessary that theretrofit piece 145 be used solely with pre-existing retractors. Indeed,it is contemplated that the retrofit piece 145 could be used or simplymodified for use with new and currently non-existing retractors.Alternatively, the anti-twist inserts 145 can be installed intopre-existing guide slots in barrier housings or other similarstructures, to prevent twisted webbing from passing into the barrierhousing and becoming wound onto a retractor spool.

Referring now to FIGS. 15-17, a third embodiment of a housing 210 for aretractor is shown. The housing 210 is a barrier-type housing, similarto that disclosed in U.S. patent application Ser. No. 11/847,435, whichhouses multiple, internally-mounted retractors for restraining awheelchair and wheelchair passenger. Specifically, two retractors areprovided for restraining a wheelchair from the rear side and threeretractors are provided for restraining a wheelchair passenger (i.e., byproviding lap and shoulder belts). The retractors include up to severalfeet of webbing, which pass through a plurality of anti-twist slots 220a, 220 b, 230 a, 230 b, 240 in the housing, so that they may beaccessible for use. Each of the slots 220 a, 220 b, 230 a, 230 b, 240include one or more anti-twist guide surfaces which may be similar tothose disclosed by the first and second embodiments. Specifically, theanti-twist lap belt slot 220 a (which is similar, identical, or a mirrorimage of the anti-twist lap belt slot 220 b) includes a left sidewallguide surface 222 a, a right sidewall guide surface 224 a, an uppersidewall guide surface 226 a, and a lower sidewall guide surface 228 a.The anti-twist rear wheelchair securement belt slot 230 (which issimilar, identical, or a mirror image of the anti-twist slot 230 b)includes a left sidewall guide surface 232 a, a right sidewall guidesurface 234 a, an upper sidewall guide surface 236 a, and a lowersidewall guide surface 238 a. The anti-twist shoulder belt slot 240 isprovided with an upper side wall guide surface 242, a lower sidewallguide surface 244, a left sidewall guide surface 226 and a rightsidewall guide surface 248. The anti-twist guide surfaces for thebarrier housing 210 can be provided with contours similar to any of theabove described guide surfaces and/or can cooperate to provide theopening with any of the various aspect ratios defined above to reducethe chance of twisted webbing from passing through the slot.

Although the inventions described and claimed herein have been describedin considerable detail with reference to certain embodiments, oneskilled in the art will appreciate that the inventions described andclaimed herein can be practiced by other than those embodiments, whichhave been presented for purposes of illustration and not of limitation.Therefore, the spirit and scope of the appended claims should not belimited to the description of the embodiments contained herein.

1. A device for reducing the chances that a twisted portion of arestraint strap will interfere with the operation of a retractorcomprising: a housing, a retractor spool, and a restraint strap, therestraint strap being wound on the retractor spool and having athickness; the housing defining an interior space in which a retractorspool is disposed and having an opening which is adapted for passing thestrap therethrough; and, the opening having an effective height which isbetween approximately two and eight times the thickness of the restraintstrap to allow a double stitched portion of the restraint strap to passtherethrough.
 2. The device of claim 1, wherein the effective height isbetween approximately two and six times the thickness of the restraintstrap.
 3. The device of claim 1, wherein the housing is a retractorcover.
 4. The device of claim 1, wherein the housing is a barrierhousing.
 5. The device of claim 1, wherein the opening is provided withat least one guide surface, the guide surface having at least one slopebetween a leading edge and a trailing edge, wherein the at least oneslope causes the leading edge to diverge from an opposing sidewall. 6.The device of claim 5, wherein the at least one slope comprises at leasta first slope near the leading edge and at least a second slope near thetrailing edge, wherein the guide surface is aligned approximatelyperpendicular to an axis of the opening near the leading edge and isaligned approximately parallel to the axis of the opening near thetrailing edge.
 7. The device of claim 6, wherein the guide surface iscurvilinear and includes a variable slope between the leading andtrailing edges.
 8. The device of claim 1, wherein the opening includes aplurality of contoured guide surfaces, at least one of which is adaptedto guide the movement of the lateral edges of the strap.
 9. The deviceof claim 1, wherein a guide surface for the opening is formed on amember which is attachable to the housing, the guide surfaceconstricting a size of the opening to provide the opening with theeffective height.
 10. The device of claim 9, wherein the member includesat least one locking groove whereby the member can be engaged with theopening by snapping into place.
 11. The device of claim 1, wherein theopening is generally quadrangular and includes four walls, onto one ofwhich at least one guide surface is formed.
 12. A device for reducingthe chances that a twisted portion of a restraint strap will interferewith the operation of a retractor comprising: a housing, a retractorspool, and a restraint strap, the restraint strap being wound on theretractor spool and having a thickness; the housing defining an interiorspace in which a retractor spool is disposed and having an opening whichis adapted for passing the strap therethrough; the opening having atleast one sidewall, with at least a portion of the sidewall having aguide surface, the guide surface being configured to guide the movementof the strap and thereby resist the passing of a twist in the strapthrough the opening and into the housing; and, the guide surface havinga leading edge and a trailing edge, the guide surface extending adistance into the opening whereby the trailing edge is disposed withinthe interior space of the housing.
 13. The device of claim 12, whereinthe housing is a retractor cover.
 14. The device of claim 12, whereinthe housing is a barrier housing.
 15. The device of claim 12, whereinthe trailing edge of the guide surface is disposed in close proximity tothe retractor spool.
 16. The device of claim 12, wherein the guidesurface has at least one slope between the leading edge and the trailingedge, wherein the at least one slope causes the leading edge to divergefrom an opposing sidewall.
 17. The device of claim 16, wherein the atleast one slope comprises at least a first slope near the leading edgeand at least a second slope near the trailing edge, wherein the guidesurface is aligned approximately perpendicular to an axis of the openingnear the leading edge and is aligned approximately parallel to the axisof the opening near the trailing edge.
 18. The device of claim 12,wherein the guide surface is curvilinear and includes a variable slopebetween the leading and trailing edges.
 19. The device of claim 12,wherein the opening includes a plurality of contoured guide surfaces, atleast one of which is adapted to guide the movement of the lateral edgesof the strap.
 20. The device of claim 12, wherein the guide surface forthe opening is formed on a member which is attachable to the housing.21. The device of claim 20, wherein the member includes at least onelocking groove whereby the member can be engaged with the opening bysnapping into place.
 22. The device of claim 12, wherein the opening isgenerally quadrangular and includes four walls, onto at least one ofwhich the guide surface is formed.
 23. A device for reducing the chancesthat a twisted portion of a restraint strap will interfere with theoperation of a retractor comprising: a housing, a retractor spool, and arestraint strap, the restraint strap being wound on the retractor spooland having a thickness; the housing defining an interior space in whicha retractor spool is disposed and having an opening which is adapted forpassing the strap therethrough; the opening having an effective heightwhich is between approximately two and eight times the thickness of therestraint strap to allow a double stitched portion of the restraintstrap to pass therethrough; the opening having at least one sidewall,with at least a portion of the sidewall having a guide surface, theguide surface being configured to guide the movement of the strap andthereby resist the passing of a twist in the strap through the openingand into the housing; and, the guide surface having a leading edge and atrailing edge, the guide surface extending a distance into the openingwhereby the trailing edge is disposed within the interior space of thehousing.
 24. The device of claim 23, wherein the effective height isbetween approximately two and six times the thickness of the restraintstrap.
 25. The device of claim 23, wherein the housing is a retractorcover.
 26. The device of claim 23, wherein the housing is a barrierhousing.
 27. The device of claim 23, wherein the trailing edge of theguide surface is disposed in close proximity to the retractor spool. 28.The device of claim 23, wherein the guide surface has at least one slopebetween a leading edge and a trailing edge, wherein the at least oneslope causes the leading edge to diverge from an opposing sidewall. 29.The device of claim 28, wherein the at least one slope comprises atleast a first slope near the leading edge and at least a second slopenear the trailing edge, wherein the guide surface is alignedapproximately perpendicular to an axis of the opening near the leadingedge and is aligned approximately parallel to the axis of the openingnear the trailing edge.
 30. The device of claim 29, wherein the guidesurface is curvilinear and includes a variable slope between the leadingand trailing edges.
 31. The device of claim 30, wherein the openingincludes a plurality of contoured guide surfaces, at least one of whichis adapted to guide the movement of the lateral edges of the strap. 32.The device of claim 30, wherein a guide surface for the opening isformed on a member which is attachable to the housing, the guide surfaceconstricting a size of the opening to provide the opening with theeffective height.
 33. The device of claim 32, wherein the memberincludes at least one locking groove whereby the member can be engagedwith the opening by snapping into place.